Stoichiometric characteristics and homeostasis of leaf nitrogen and phosphorus responding to different water surface elevations in hydro-fluctuation zone of the Three Gorges Reservoir

Abstract

As a type of wetland ecosystem with off-season 30 m water level fluctuation, the huge changes in the ecological environment, plant species, and vegetation dynamics in the hydro-fluctuation zone of the Three Gorges Reservoir (TGR) area have attracted a wide range of attention. In this present study, six typical locations in the water level fluctuating zone were used as the research objects, and the effects of different water surface elevations on the stoichiometric characteristics and homeostasis of leaf nitrogen and phosphorus were studied through a sample survey method. Results revealed that leaf nitrogen content was linearly correlated with leaf phosphorus content along water surface elevation. And water surface elevation significantly affected the nitrogen and phosphorus content of dominant plants. Four dominant species [Cynodon dactylon (Linn.) Pers, Xanthium sibiricum Partin ex Wider, Abutilon theophrasti Medik, and Bidens pilosa Linn] exhibited specific differences in the phosphorus steady state index (Hp) and nitrogen steady state index (HN). Although belonging to different categories, both HP and HN of four dominant species were in the same order: X. sibiricum > A. theophrasti > C. dactylon > B. Pilosa. The interspecific differences in HN and HP indicated that there were differences in the characteristics of nutrient utilization of dominant species and their adaption to water surface elevation. Furthermore, as the elevation increases, the community coverage increased and the community stability index also increased. This might indicate that in the fluctuating zone habitat, the plant’s nitrogen and phosphorus utilization strategy affects the distribution and composition of plant community along water surface elevation, and ultimately affects the stoichiometric homeostasis on the community levels.